Apparatus for aperture controlled electrostatic image reproduction or constitution

ABSTRACT

The invention basically comprises apparatus and methods relating to the field of electrostatics, and is concerned with electrostatic reproducing or constituting. Apertured screen means carry charge distributions in accordance with a pattern such that particles directed at the screen means pass therethrough under modulation control dictated by the pattern. The invention further relates to apparatus and methods for constituting or reproducing images through the use of a multilayered screen consisting of an array of apertures. A propulsion field directs charged particles through the screen to a receiving medium preferably spaced at a distance from the screen. Charge distribution on the screen controls the flow of particles through the apertures, some of which are in effect blocked, partially blocked, unblocked, and enhanced, depending on the local charge level. Thus, it is possible to produce patterns of varying tone without contact with the printed or effected substrate. The screen preferably consists of a conductive layer and an insulative layer for supporting opposite charges across the insulative layer. A uniform charge level or field may be established across the insulator layer and then modified in accordance with an image to be reproduced by selectively counteracting and reversing the field through the selective application of a second field of greater magnitude. Novel contact field charging may also be used to modify the first field or precharge. Imaging elements comprising a transparent support, transparent conductive layer, and transparent insulative layer secured together in that order are provided for contacting the screen to permit an applied voltage connected between the conductive layer of the imaging elements and the conductive layer of the screen to modify and even reverse the precharge level in accordance with image light shined through the image elements onto the screen. The screen insulator layer need not be photoconductive if the image elements include as the transparent insulative layer a photoconductive layer which need not be transparent. The imaging elements may be used with or without the enhancing field. Ions may comprise the particles to take advantage of the enhancing fields or used in conjunction with toner particles to cause printing on ordinary paper.

United States Patent Pressman et al.

[ Mar. 7, 1972 [72] Inventors: Gerald L. Pressman, San Jose; Thomas D. Kittredge, South San Francisco, both of Calif.

[73] Assignee: Electroprint, Inc., Palo Alto, Calif.

[22] Filed: Nov. 15, 1968 [21] Appl. No.: 776,146

Primary ExaminerSamuel S. Matthews Assistant Examiner-Robert P. Greiner Attomey-Townsend & Townsend ABSTRACT The invention basically comprises apparatus and methods relating to the field of electrostatics, and is concerned with electrostatic reproducing or constituting. Apertured screen means carry charge distributions in accordance with a pattern such that particles directed at the screen means pass therethrough under modulation control dictated by the pattern.

The invention further relates to apparatus and methods for constituting or reproducing images through the use of a multilayered screen consisting of an array of apertures. A propulsion field directs charged particles through the screen to a receiving medium preferably spaced at a distance from the screen. Charge distribution on the screen controls the flow of particles through the apertures, some of which are in effect blocked, partially blocked, unblocked, and enhanced, depending on the local charge level. Thus, it is possible to produce patterns of varying tone without contact with the printed or efiected substrate.

The screen preferably consists of a conductive layer and an insulative layer for supporting opposite charges across the insulative layer. A uniform charge level or field may be established across the insulator layer and then modified in accordance with an image to be reproduced by selectively counteracting and reversing the field through the selective application of a second field of greater magnitude. Novel contact field charging may also be used to modify the first field or prechargc. Imaging elements comprising a transparent support, transparent conductive layer, and transparent insulative layer secured together in that order are provided for contacting the screen to permit an applied voltage connected between the conductive layer of the imaging elements and the conductive layer of the screen to modify and even reverse the precharge level in accordance with image light shined through the image elements onto the screen. The screen insulator layer need not be photoconductive if the image elements include as the transparent insulative layer a photoconductive layer which need not be transparent. The imaging elements may be used with or without the enhancing field. lons may comprise the particles to take advantage of the enhancing fields or used in conjunction with toner particles to cause printing on ordinary paper.

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2. The apparatus of claim 1 wherein the means for supplying charged marking material is disposed on one side of the screen means and the print receiving material is disposed on the opposite side of the screen means.
 3. The apparatus of claim 2 wherein the means for diminishing and reversing the charges comprises an image station; and the means establishing the projection field comprises a printing station disposed in spaced relation to the image station along said path.
 4. The apparatus of claim 3 wherein the insulative screen layer comprises a photoconductor.
 5. The apparatus of claim 4 wherein the image station comprises a source of corona charge for the photoconductor, said means for establishing a field across the insulative screen layer comprising a transparent conductor and an adjacent transparent insulator in contact with the screen layer and connections from the transParent conductor and the screen conductive layer to a source of voltage for said field; and said means for selectively establishing comprising optical means for rendering said field selectively effective to diminish and reverse the corona charge in accordance with the image.
 6. An aperture controlled electrostatic printing system capable of controlling the flow of charged particles by the selective blocking and enhancing of particle flow in accordance with an image to be reproduced comprising in combination a multilayer screen comprising at least a screen insulator layer overlaying a screen conductive layer; means applying a potential level to the conductive layer; means for electrostatically charging the insulator layer to provide a double charge layer; means for modifying the charge of the insulator layer through zero to complete reversal in accordance with an image to be reproduced; said last-mentioned means comprising distributing means for applying a charge pattern in accordance with an image but of opposite polarity to the charge layer on the insulator layer to modify the double layer charge; means for directing charged particles through the multilayer screen in accordance with the modified charge; and means for locating a print receiving medium oppositely of the insulator layer relative to the means for directing charged particles to receive the particles passing through said multilayer screen.
 7. A system for image reproduction through the use of modulated apertures comprising, in combination a multilayer screen comprising at least a conductive screen and an insulative screen affixed thereto with the apertures coinciding; means for double charging the insulative screen; means for applying an electric potential level to the conductive screen; means for selectively discharging and oppositely charging said insulative screen in accordance with an image to be reproduced thereby establishing blocking fields in selected apertures of said screen and enhancing fields in other apertures thereof; said last-mentioned means comprising a source of electrical charging capable of applying to the insulative screen charge levels of opposite polarity and approximately double magnitude relative to said double charging thereof, and optical means for modifying the magnitudes of said charge levels in accordance with an image to be reproduced to establish said blocking and enhancing fields; source means for charged particles; and means for transferring the charged particles via partially blocked, unblocked, and enhanced apertures in greater density in that order to receiving material.
 8. In apparatus for electrostatic printing, the combination comprising a multilayer screen including at least a screen insulator layer overlaying a screen conductor layer, means drivingly mounting the screen for endless conveyor-type movement; means maintaining the conductor layer at a fixed potential; means for charging the insulative layer with equal and opposite charges to produce uniform electric fields in the apertures thereof; means for modifying the fields including magnitude and polarity in selected apertures determined by an image to be reproduced to produce a modified field image pattern; said modifying means comprising means for introducing to the charged screen potential of polarity opposite to said charges and of a magnitude greater than the magnitude of said charges; means for charging marking material; means moving the modified field image pattern from the charging region by movement of the screen; means registering print receiving material opposite the so-moved modified field image pattern; and means for projecting marking material toward the screen for passage through the modified field image pattern in accordance with the fields of the apertures to the print receiving material.
 9. The apparatus of claim 8 wherein the means for modifying comprises a transparent insulator, a transparent conductor in contact therewith, and a transparent support for the conductor and insulator, and the means introducing electric potential includes connections to the transparent conductor and the conductor layer; and further comprising optical means for shining the image as a light pattern onto the screen insulator layer via the transparent support, conductor and insulator.
 10. Apparatus for providing an electrostatic image charge pattern for use in electrostatic printing comprising, in combination transparent support means, transparent conductive means, and transparent insulator means, all sandwiched together to comprise image plate means for transferring an image pattern; apertured screen means comprising a photoconductor layer and a conductor layer; means maintaining the screen conductor layer at a fixed potential; means for pressing the elements sandwiched together against the apertured screen means with the insulator means in contact with the photoconductor layer; and means for applying an electric field between the transparent conductive means and the screen conductor layer to transfer the image pattern to the screen means.
 11. The apparatus of claim 10 further comprising means for applying substantially uniform electrical charge to the photoconductor layer prior to contact with the insulator means.
 12. Apparatus for electrostatic printing comprising in combination a screen having a photoconductive layer and a conductive layer; means establishing forward and reverse fields in the screen apertures varying in magnitude and polarity in accordance with the density of an image to be reproduced; said last-mentioned means comprising means for establishing a first field as a uniform charge level across the photoconductive layer; means for producing a charge level greater than, and in opposition to, said first field, and optical means for selectively modifying the charge level in accordance with an image to be reproduced and impressing the modified charge level across the photoconductive layer; means supplying charged particles which would be blocked by only one of the forward and reverse fields; means establishing a propulsion field from one side of the screen to the other side of the screen for the charged particles; and locating means for positioning print receiving means to intercept particles which pass through the screen.
 13. The apparatus of claim 12 wherein the optical means flash a positive print image onto the photoconductive layer.
 14. The apparatus of claim 13 wherein the optical means flash a negative image onto the photoconductive layer.
 15. An aperture controlled electrostatic printing system comprising in combination a multilayer screen comprising at least a screen insulator layer overlaying a screen conductive layer; means applying a potential level to the conductive layer; means for double charging the insulator layer with charges varying from one polarity through zero to reverse polarity in accordance with an image to be reproduced; said last-mentioned means comprising means for establishing charges of a first polarity on the screen insulator layer and charging means; said charging means comprising at least adjacent transparent dielectric material and transparent conductive material, and a source of potential connected to the transparent conductive material and to the screen conductive layer of polarity opposite to said first polarity and of a magnitude greater than said charges; at least one of said insulator screen layer and dielectric material comprising photoconductive material, and optical means for directing light in accordance with an image through the charging means onto the screen insulative layer to enable the screen insulative layer polarity selectively to be reversed; means for directing charged printing material through the charged multilayer screen in accordance with the charges thereon to control the density of passage of printing material; and means for locating a print receiving medium oppositely of the insulator layer relative to the means for directing charged printing material to receive the printing material passing through said multilayer screen.
 16. An aperture controlled electrostatic printing system comprising in combination a pair of multilayer screens each comprising at least a screen insulator layer overlaying a screen conductive layer; means for charging the insulator layer of the first screen with charge levels varying in accordance with an image to be reproduced; means for uniformly charging the insulator layer of the second screen; means for directing ions through the first screen in accordance with the charge levels thereon to the second screen to modify the uniform charging thereof in accordance with the image to be reproduced with the modified charge levels varying from one polarity through zero to reverse polarity; and means for locating a receiving medium to be printed from said second screen.
 17. An aperture controlled electrostatic printing system comprising a screen means comprising an array of apertures; said screen means characterized by the ability to carry charge patterns establishing forward and reverse fields within the apertures in accordance with an image to be reproduced; means for establishing said forward and reverse fields selectively distributed across said screen means in accordance with said image; and means for directing charged particles through the charged screen means in accordance with the charge pattern thereon to control the density of passage of the particles.
 18. An aperture controlled electrostatic printing system comprising a screen means comprising an array of apertures; said screen means characterized by the ability to carry charge patterns establishing forward and reverse lines of force extending into the apertures; means for establishing said lines of force selectively distributed across said screen means in accordance with an image; means for directing charged particles from a source through the charged screen means in accordance with the charge pattern thereon to control the density of passage of the particles; and means for locating a receiving medium oppositely of the source of the particles to receive the particles passing through said screen means.
 19. An aperture controlled electrostatic printing system comprising screen means comprising an array of apertures; said screen means characterized by the ability to carry charge patterns establishing lines of force extending into the apertures which electrically close and electrically open apertures in varying degrees from complete closure to opening even beyond their physical dimension in accordance with an image; means for establishing said charge patterns selectively distributing said lines of force across said screen means in accordance with said image; means for directing charged particles of an electrical sign to pass through the electrically open apertures through the screen means in accordance with the closed and opened apertures therein to control the density of passage of the particles; and means for locating a receiving medium oppositely of the means for directing charged particles to receive the particles passing through said screen means directly from the means for directing charged particles.
 20. An aperture controlled electrostatic system comprising screen means comprising an array of apertures; said screen means characterized by the ability to carry charge distributions establishing forward and reverse fields within the apertures in accordance with a pattern to be reproduced; means establishing forward charge fields within the apertures; means for establishing reverse charge fields within the apertures; means selectively applying to said screen means said means for establishing reverse charges as to aperture locations and charge magnitudes according to said pattern; and means for directing charged particles through the charged screen means in accordance with the distributions thereon to control the density of passage of the particles.
 21. An aperture controlled electrostatic system comprising screen means comprising an array of apertures; said screen means charaCterized by the ability to carry charge distribution establishing forward and reverse lines of force extending into the apertures; means establishing forward lines of force within the apertures; means for establishing reverse lines of force within the apertures; means selectively applying to said screen means said means for establishing reverse lines of force as to aperture locations and lines of force magnitude according to said pattern; means for directing charged particles from a source through the charged screen means in accordance with the charge distribution thereon to control the density of passage of the particles; and means for locating a receiving medium oppositely of the source of the particles to receive the particles passing through said screen means.
 22. An aperture controlled electrostatic printing system comprising screen means including an array of apertures; said screen means comprising an insulator characterized by the ability to carry charge patterns establishing forward and reverse fields within the apertures in accordance with an image to be reproduced; contact charging means comprising transparent conductive means and photoconductive means for contact with the insulator to charge the insulator in accordance with the image by establishing said fields; and means for directing charged particles through the charged screen means in accordance with the charge pattern thereon to control the density of passage of the particles.
 23. An aperture controlled electrostatic printing system comprising in combination a multilayer screen comprising at least a screen insulator layer overlying a screen conductive layer; means applying a potential level to the conductive layer; photoconductive means for double charging the insulator layer with charges varying from one polarity to zero in accordance with an image to be reproduced; means for directing charged printing material through the charged multilayer screen in accordance with the charges thereon to control the density of passage of printing material; and means for locating a print receiving medium oppositely of the insulator layer relative to the means for directing charged printing material to receive the printing material passing through said multilayer screen.
 24. An aperture controlled electrostatic printing system comprising in combination a multilayer screen comprising at least a screen insulator layer overlying a screen conductive layer; photoconductive means for double charging the insulator layer with charges varying from one polarity to zero in accordance with an image to be reproduced; means for directing charged particles through the charged multilayer screen in accordance with the charges thereon to control the density of passage of the particles; and means for locating a receiving medium to receive the particles passing through said multilayer screen.
 25. An aperture controlled electrostatic printing system comprising a screen means having an array of apertures; said screen means comprising an insulator characterized by the ability to carry charge patterns establishing fields within the apertures in accordance with an image to be reproduced; contact charging means comprising transparent conductive means and photoconductive means for contact with the insulator to charge the insulator in accordance with the image; and means for directing charged particles through the charged screen means in accordance with the charge pattern thereon to control the density of passage of the particles.
 26. An aperture controlled electrostatic printing system comprising a screen means including an array of apertures; said screen means comprising an insulator characterized by the ability to carry charge patterns establishing forward and reverse lines of force extending into the apertures; contact charging means comprising transparent conductive means and photoconductive means with the latter means in contact with the insulator to charge it in accordance with the image by establishing said forward and reverse liNes of force; means for directing charged particles from a source through the charged screen means in accordance with the charge pattern thereon to control the density of passage of the particles; and means for locating a receiving medium oppositely of the source of the particles to receive the particles passing through said screen means.
 27. An aperture controlled electrostatic printout system comprising screen means having an array of apertures; said screen means comprising insulating means characterized by the ability to carry charge patterns establishing positive through negative fields selectively within the apertures in accordance with an image to be reproduced; charging means for the screen means comprising transparent conductive means and photoconductive means for deployment in contact with the screen means with the photoconductive means against the insulating means to apply said charge patterns to the insulating means; and means for directing charged particles through the charged screen means in accordance with the charge pattern thereon to control the density of passage of the particles.
 28. Aperture controlled printing apparatus comprising image projection means; apertured screen means capable of carrying charge patterns establishing lines of force extending into the apertures; means for precharging the screen means prior to exposure by the image projection means to establish said lines of force; means selectively modifying said lines of force by opposed lines of force to reduce, cancel and reverse the lines of force effective in the apertures in accordance with said image; and means for developing an image pursuant to the charges on the screen.
 29. Aperture controlled printing apparatus comprising apertured screen means capable of carrying fields effective within the apertures; image projection means for flashing an image to be reproduced upon the screen; means hingeably connected to the screen means for locating a receiving medium adjacent thereto; said means hingeably connected comprising a projection electrode; means for establishing a projection field via the screen means to the projection electrode; and means for developing the image on the receiving means by introducing toner particles to the projection field; said projection electrode being movable away from the screen means to permit flashing of said image thereon and movable adjacent to the screen means to permit development of the image.
 30. The apparatus of claim 29 further comprising charging means hingeably connected to the screen means for modifying said fields.
 31. The apparatus of claim 29 further comprising means for charging the screen means with a uniform precharge.
 32. An aperture controlled electrostatic printing system comprising screen means including an array of apertures; said screen means characterized by the ability to carry charge patterns establishing lines of force extending into the apertures which electrically close and electrically open apertures in varying degrees from complete closure to opening even beyond their physical dimension in accordance with an image; means for uniformly charging the screen means; means for charging the screen means to said charge patterns in accordance with said image; means for directing ions through the screen means in accordance with the closed and opened apertures therein too control the density of passage of the ions; and means for locating a receiving medium to receive the ions passing through said screen means.
 33. The system of claim 32 further comprising means for developing the ion pattern on the receiving medium.
 34. An aperture controlled electrostatic printing system comprising first and second screen means each comprising an array of apertures; at least said second screen means characterized by the ability to carry charge patterns establishing forward and reverse lines of force extending into the apertures; means for charging the first screen means in accordance with an image; means for uniformly charging the seconD screen means; means for directing ions from a source through the charged first screen means in accordance with the charge pattern thereon to the second screen means to establish said charge patterns; means for locating a receiving medium oppositely of the second screen means; and means for directing marking material through said second screen means to the receiving medium.
 35. The system of claim 34 wherein the means for charging the first screen means comprises a source of uniform charge for the screen means.
 36. Electrostatic printing screen means comprising a plurality of conductors to define an array of apertures, and insulation on the conductors covering only a portion of their surfaces; and said insulation defining a peripheral opening of each aperture; the ratio of the thickness of the insulation on the conductors to the diameter of the apertures being less than one.
 37. The screen means of claim 36 wherein said surfaces comprise approximately one-half of each conductor.
 38. The screen means of claim 36 wherein said surfaces are oriented in a common direction; and said plurality of conductors comprises a conductive plate having holes therethrough to form said apertures. 